Robert James Mills appeared in the Invercargill District Court yesterday for assaulting his mother with a lettuce.

Police said Mills, 37, was arguing with his mother at an Invercargill property on February 16 when he uplifted the lettuce from the garden and threw it at her, "connecting with the victim's face and taking her by surprise".

Defence lawyer Scott Williamson said the lettuce incident was the result of an ongoing argument between the pair.

Judge Alistair Garland said Mills' actions appeared to be borne by frustration.

"It didn't cause any physical injuries but the friction between the two of you is causing emotional harm and it's something you need to address," he said.

He sentenced Mills to nine months' supervision on the condition he undertake counselling for alcohol, drug and anger issues if directed by the probation service.